Conventionally, for data tracks on a magnetic disk medium in a magnetic disk device such as a hard disk drive (HDD), a spiral data track system is available in which the data tracks are arranged in a spiral form from an outer circumference towards an inner circumference of the disk medium or from an inner circumference towards an outer circumference thereof so as to improve sequential access performance of the head of the disk device.
In a spiral data track system, for example, when a head is made to follow data tracks in a spiral form from an outer circumference towards an inner circumference, the head moves from the outer circumference towards the inner circumference. Accordingly, when controlling the head to follow part of the tracks repeatedly, it is necessary to perform a seek operation at the time when the head directed towards the center is returned towards the outer circumference. This may cause a waiting time for the head after being settled by the seek operation to reach a start point where it starts reading or writing data.